I have no idea which Itachi you're talking about so I can't really say for certain. If it was Itachi Uchiha, then I'd say that Itachi could probably take Gaara since Gaara could only tie with Naruto and Itachi can beat Naruto. So it would be between Itachi and Vegeta. I would have to go with Itachi on that one because of the powers of his Sharingan. Sorry Vegeta but you're still in second place. lol "You can only be young once, but you can be immature forever! "

garra because he could fall asleep and turn into the wind demon and crush everyone. the first to go would be itachi then garra and vegeta would have an all out brawl wile vegeta is in giant monkey form.... Skatch that Vegeta would win "How unexpectedly irregular. Why do you continue to resist?" - Gurren Lagann, Anti-Spiral

Vegeta because come on he can fly, shoot beams of pure energy, and he can go ssj4. gaara's ultimate defence would crumble at the big bang attack and itachi isn't fast enough to keep up with him and would be destroyed by the final shine attack.